The field of the invention relates generally to power conversion, and more particularly, to a power converter and methods of increasing power delivery from soft AC power sources.
Telecommunications and other direct current (DC) based power plants typically use multiple alternating current (AC) and/or DC power sources to provide power to a load. At least some known AC power sources use rectifiers to convert AC output voltages to a regulated DC output, and at least some known DC power sources use DC-DC converters to adjust their voltage levels to a regulated DC output. A DC bus aggregates the DC outputs and enables them to power the load. The rectifiers and/or the DC-DC converters are typically managed by a system controller that allocates the load among the multiple power sources.
In system applications, rectifiers may receive AC power from the grid or from “soft” AC sources. A soft AC input power source is a source having a limited current sourcing capability, in that a large enough load at an output of a power converter can draw down the input voltage and cause the source to shutdown, go into current limiting, become unstable, oscillate, or trip an input detector. For example, a soft AC power source is one that cannot deliver enough current to clear a 20-30 Amp input threshold, or delivers a current that is less than 5% of a maximum tolerated range. Soft AC input power sources may include, but are not limited to including, a diesel generator (also referred to as a “genset”), an inverter, a wind-powered generator, or any other fuel-powered generator. Such soft AC input power sources are configured to leave excess source capacity on tap for reliable operation. When the soft source is a genset, a sum of rectifier loads, battery recharge, and other loads, such as air conditioner/heating loads is typically sized not to exceed about 80% of the genset rating at sea level. As a result, recharge rate is limited and generator run times are extended when air conditioning/heating is not needed. Extended run times cause waste of fuel. A similar soft source problem occurs when rectifiers run off wind-powered generators where the source is variable over time as the wind speed changes.